Parents say the rare polio-like illness, Acute Flaccid Myelitis, affecting children across the U.S. is being underreported.

At least two families say they lost their sons to AFM.

Both children had been paralyzed from the neck down before they died.

The CDC claims there have been no AFM deaths this year.

"The reporting of the diseases has a lot of steps,” says Dr. Anne Schuchat, principal deputy director with the CDC. “So, there may be a lag. We are working 24/7 to increase recognition, to get the reporting into the system. Every one of these episodes is difficult and the deaths are really tragic."

CDC medical advisors say the lag is too long, and that the turnaround should be faster.

AFM affects the spinal cord and could cause paralysis.

Almost all cases have been found in children under the age of 18.

The CDC says the agency is working hard to find the cause of the outbreak.